Face masks find utility in a variety of medical, industrial and household applications by protecting the wearer from inhaling dust and other harmful airborne contaminates through their mouth or nose. Likewise, the use of face masks is a recommended practice in the healthcare industry to help prevent the spread of disease. Face masks worn by healthcare providers help reduce infections in patients by filtering the air exhaled from the wearer thus reducing the number of harmful organisms or other contaminants released into the environment. Additionally, face masks protect the healthcare worker by filtering airborne contaminants and microorganisms from the inhaled air.
The section of the face mask that covers the nose and mouth is typically known as the body portion. The body portion of the mask may be comprised of several layers of material. At least one layer may be composed of a filtration material that prevents the passage of germs and other contaminants therethrough but allows for the passage of air so that the user may comfortably breathe. The porosity of the mask refers to how easily air is drawn through the mask. A more porous mask is easier to breathe through. The body portion may also contain multiple layers to provide additional functionality or attributes to the face mask. For example, many face masks include one or more layers of material on either side of the filtration media layer. Further components may be attached to the mask to provide additional functionality. A clear plastic face shield intended to protect the user's face from splashed fluid is one example.
As stated, face masks may be designed to be resistant to penetration by splashes of fluids so that pathogens found in blood or other fluids may not be able to be transferred to the nose, mouth, and/or skin of the user of the face mask. The American Society of Testing and Materials has developed test method F-1862, “Standard Test Method of Resistance of Medical Face Masks to Penetration by Synthetic Blood (Horizontal Projection of Fixed Volume at a Known Velocity)” to assess a face mask's ability to resist penetration by a splash. The splash resistance of a face mask is typically a function of the ability of the layer or layers of the face mask to resist fluid penetration, and/or their ability to reduce the transfer of the energy of the fluid splash to subsequent layers, and/or by their ability to absorb the energy of the splash. Typical approaches to improving fluid resistance are to use thicker materials or additional layers in the construction of the face mask. However, these solutions may increase the cost of the face mask and reduce the porosity of the face mask.
Referring to the prior art configuration of FIGS. 1 and 2, the body portion 12 of face masks 10 are typically manufactured with horizontal folds 22 and 26 so that the body portion 12 may be adjusted vertically or otherwise to allow the body portion 12 to be formed into a chamber with the perimeter of the chamber sealing to the face of the user. All of the layers 20 and 24 of the body portion 12 are folded simultaneously during manufacture of the face mask 10. Creases 56 and 58 in the layers 20 and 24 of the body portion 12 are therefore nested or aligned with one another both before unfolding of the body portion 12, as shown in FIG. 1, and after unfolding as shown in FIG. 2. It is sometimes the case that the layers 20 and 24 are adhered to one another before folding. Folding of the layers 20 and 24 independently from one another is not done as this technique allegedly adds cost and complexity to the manufacturing process.
Inspection of face masks 10 that fail to meet certain criteria of the F-1862 method has shown a higher rate of failure when fluid impacts the creases 56 and 58 that are placed into the body portion 12. The folding process weakens the body portion 12 at the creases 56 and 58 and in turn makes this area more susceptible to fluid penetration. Additionally, the completely nested configuration of the creases 56 and 58 brings the individual layers 20 and 24 together with one another thus allowing more energy and fluid to be transferred from one layer to the next during a fluid splash.